Physical measurement of a slow drag of a drag embedment anchor during sea trials
Harnois, Violette; Parish, D; Johanning, Lars
Date: 17 October 2012
Publisher
ICOE
Abstract
Anchor drag during operation of offshore structures
could significantly alter the initial load design
characteristics of a mooring system. Hence an
estimation of anchor positions during operation is
essential to identify whether slow or abrupt anchor
motion occurs and might require the redeployment
of an anchor.
During storm ...
Anchor drag during operation of offshore structures
could significantly alter the initial load design
characteristics of a mooring system. Hence an
estimation of anchor positions during operation is
essential to identify whether slow or abrupt anchor
motion occurs and might require the redeployment
of an anchor.
During storm conditions, monitoring of mooring
tensions and structure motions at the South West
Mooring Test Facility (SWMTF) revealed the slow
drift motion of one anchor. This facility is a surface
buoy with a three-legged, compliant mooring system
designed to investigate mooring system behaviour
for Marine Renewable Energy (MRE) devices. This
paper presents i) some methods to identify the
deployment anchor positions: numerical model,
acoustics diver survey, and towed sonar ii) the
analyses procedure, and estimations of slow drift
anchor motion.
The findings indicate that one drag embedment
anchor moved slowly during a moderate but
prolonged and isolated storm, before embedding
again. The work demonstrates that anchor position
can be accurately monitored and that anchor
motion is not necessarily due to excessive peak
loads.
Engineering
Faculty of Environment, Science and Economy
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